APPARATUS AND METHOD FOR SORTING OBJECTS

DESCRIPTION

Prior Art

The first modern sorting machine (early 1930's) consisted of a moving conveyor belt on which grains of rice to be sorted where placed. The operator could adjust the feed speed of the belt and was also equipped with a flexible tube coupled to a centrifuge pump connected to a sorting cyclone. The operator manually moved the tube towards the non-compliant grains, thus eliminating them by suction and sorting in the cyclone. Such machine, in addition to being labour- intensive, does not ensure high or reliable sorting standards in time. The progress of consumptions spurred the need to improve sorting techniques.

Additionally, sorting needs evolved during the years, to include the sorting of cereal grains, in particular of durum wheat. Such demand is determined by the need of durum wheat flour production companies to standardise the colour of the extruded pasta and increase its organoleptic features.

The first sorting machines based on photoelectric devices allowing full automation and sorting control were made during the 1980's mainly by Sortex. US patents US 4,513,868; US 4,630,736; US 4,699,273; and US 5,873,470 are the most significant examples of intellectual property developed in this field.

The machine was devised so as to convey the grains one by one to a slide which let them drop onto a lighting system. The light reflected by the grain was focused by means of an optical assembly, consisting of filters and focusing lenses, onto a photocell assembly. The signals output by the photocells were electronically compared against a sample signal representing a standard grain. When an anomalous signal was found, the electronic system opened a solenoid valve which sent a jet of compressed air that deviated the grain onto a conveying channel communicating with a collection silos. Such technology was limited in terms of detection accuracy and sorting speed.

In the course of year 2000, new sorting technologies based on optical detectors whose images were processed by microcomputers were introduced.

Such machines were based on the use of particularly sensitive multiple colour TV cameras which allow to detect defects even smaller than 0.3 mm. The TV cameras replace the use of photocells allowing sorting nine times more refined and faster than that of the earlier photocell machines. The mechanics used to convey grains to the viewing and non-compliant ejecting assembly remained essentially identical to that of the photocell machine.

In the optical sorting machine, the grains were illuminated by a light having an appropriate wavelength and then viewed by a TV camera provided with a processor which analysed the image and sent, if required, the signal to a pneumatic solenoid valves to eject the non-compliant groups of grains. Such a machine can currently identify grains with black spots, decolouration, unripe green grains, yellow and burnt grains, incompletely dehulled grains, gravel and glass fragments.

US Patents 6,427,128 and 5,917,927 by Satake Corporation are some examples of intellectual property developed in this field.

Summary of the Invention

The invention to which this patent is related aims at seeking faster speed and lower cost methods for characterising granular objects in general, and cereals or grains or seeds in particular. The invention is based on recent electronic technology developments and printed circuit technology allowing to compete with the current technologies and open an investigation niche which is unexplored to date in the state of the art of this field.

Indeed, recent experimental tests conducted by the present applicant (Sortron S.r.l.) have shown how impedimetric analysis performed singularly on single objects may open new horizons to the classification of objects obtaining very marked results in object classification. In particular, impedimetric analysis, as shown in the details of the invention, allows to relate conformational features of the single object, such as volume and shape, to the signal generated by said impedimetric measurements.

Finally, the combined and crossed analysis of optical measurements and impedimetric measurements on the single object in a continuous flow have proven to exceed in sorting quality (in particular for grains) those of the state of the art. The main advantages of the present invention consist in the very high discriminatory capacity and the high degree of parallelism, capable of processing large amounts of material on production lines. The use of integrated electronic systems also allows high operative speed, easy calibration and flexibility to the required classification features. Summarising, the advantages of the approach, in the specific case of grain sorting, are: 1) Sorting: the sorting machine allows to obtain, thanks to the previously described crossed analysis process, a product in which the different typologies of objects (specifically, grains) are discriminated and differentiated with very low percentages of error with respect to the sorting output of competing machines currently used in the milling industry; 2) Flexibility: the possibility of using variable selective parameters allows to adapt sorting criteria to the grain batch under investigation; the sorting algorithm which manages the discrimination process and the various types of grains, and therefore the machine output, is actually programmable via software in an entirely flexible manner; 3) Rejected product recovery: three-dimensional characterisation of each grain offered by the system allows a rather efficient use in the recovery of good grain from a rejected product than other sorting machines; and

4) Competitive costs: the structural components of the proposed structure can be made by exploiting widely used materials (the external structure is metallic, the internal piping system is made of plastic). The electronic system itself uses very low cost components and exploits standard PCB (printed circuit board) technology.

Brief description of the drawings A detailed description of a preferred embodiment of the apparatus and method for sorting objects of the present invention will be given hereinafter, as a non limiting example, and with reference to the annexed drawings, wherein:

Figure 1 shows a device with guides for conveying the flow of objects with integrated electronic systems;

Figure 2 shows the device of Figure 1 in frontal/cross-sectional view, wherein there are shown an electromagnetic sensor consisting of electrodes P1 and P2, an electronic signal generation system ES, and an optical sensor consisting of an emitter L and a receiver IR;

Figure 3 is a frontal/cross-sectional view of the device of Figure 1 showing the interaction with the electromagnetic field EF generated by electrodes P and the possibility of moving objects by using a conveyor CR; Figure 4 is a top view of the device of Figure 1 showing the interactions with the electromagnetic field EF generated by electrodes P with objects of different conformational structure;

Figure 5 shows the device in Figure 1 in a side view thereof;

Figure 6 shows a functional embodiment of an apparatus for sorting objects according to the present invention;

Figure 7 shows a schematic representation of the circuit control of each electronic system (ES);

Figure 8 shows an electronic oscillator controlled by the electric capacitance established between the metallic electrodes P1 and P2 positioned near guides of the apparatus according to the present invention;

Figure 9 shows a light radiation receiver reading circuit;

Figure 10 shows a controlling system for a multi-channel apparatus wherein each channel includes several electronic system and interacting with the ejection systems (EJ) and the management systems (MC, CH) of the apparatus according to the present invention; and

Figure 11 shows an example of statistic classification of various subcategories of objects detected according to the output of optical sensors (left diagram) and impedimetric sensors (right diagram).

Detailed description of the Invention

With reference now to Figure 1 and as claimed in the present application the invention is based on a multi-sensorial characterisation, and more specifically on

crossed optical and impedimetric analysis of the objects to be sorted. Parallel guides (W), also called channels, are created on a slanted plant support (B).

The objects to be sorted are immersed in a continuous, free-falling flow along said guides. The support may be made using generic printed circuit board (PCB) technology which allows to obtain structures with excellent mechanical features, and the possibility of integrating electronic circuits and cost-effective production. A flow of objects (S) proceeds in direction (F) without obstacles of mechanical origin, possibly and preferably in a reciprocally disjoined fashion. To help this condition, a mechanical apparatus (M) facilitates introduction and defines the falling frequency of single objects.

One or more electronic systems (ES) arranged at predetermined positions on each guide line, without interfering with the descending flow, classify the single objects on the basis of their physical and/or geometric features. The electronic systems may be made on the same sliding support (B) or on separate bases containing the single electronic components (EC) and connected to the base by means of specific adapters (A).

With reference now to Figure 2, the presence of two sensorial typologies is highlighted, whose data will be processed in real-time by cross-correlation. In particular, the object is optically analysed by an optical radiation emitter (L) and by a receiver (IR) arranged near the guide line. Without limitations of generality, the emitter may be positioned either on the opposite side of the receiver (as shown in Figure 2) for transmission analysis; or on the same side as the emitter by reflecting analysis of the radiation. The receiver may be positioned in a compartment underneath the guide (W) and inserted in an opening (H) which allows the reception of the light signal. In addition to the above, the two optical detection systems (for transmission and for reflection) may be combined in a structure having one emitter and two receivers, one of which is placed on the same side as the emitter and one is positioned on the opposite side.

In all of the described structures, in order to avoid interference with the surrounding environment, a specific shielding (C) may be placed near the receiver and possibly also supporting the transmitter. Optical analysis is made by an electronic circuit (IRC in Figure 11) capable of detecting and amplifying the signal

from the receiver. Entirely independently from above, one or more impedimetric type analysis will be performed on the descending objects. The single object is subjected to a superficial electronic field generated by one or more electrodes (P) connected to electronic circuits (EC) and arranged near the guides. The relationship between voltage applied to the electrodes and respective induced current determines a characterisation of the object (S) susceptible to classification.

The arrangement of electrodes may be made following different typologies to optimise performance and to adapt to the structures of the objects themselves. In this case, the electrodes, made by simple PCB technology metallization may be extended towards the deeper part of the cavity with conductive paints or may remain on the surface.

A simple, but not exclusive, methodology for determining impedimetric features of the single object are shown in Figure 2 and Figure 8. The above- mentioned electrodes constitute the armatures of an electrical capacitor which constitutes the characteristic reactance of an oscillator (OC). Said armatures form an electrical field which intersects the guides. As better shown in Figure 4, the passage of the single object in said guides determines a perturbation of said electrical field inducing a variation of the aforementioned electric capacitance and the characteristic frequency of said oscillator. The oscillator frequency is therefore the index of some conformational features of the grain itself, such as volume, material features and shape.

With reference to Figure 1 , it may be observed how different sensorial analysis types may be adopted: one or more impedimetric and/or optical sensors may be arranged or intercalated along the same guide line in order to collect the highest possible number of data. In a more compact arrangement, the impedimetric and optical sensor may share the same location. The electronic system (EC) may therefore consist of several sensorial units connected to a central unit which may consists of a micro-controller (LC) as shown in Figure 7. Furthermore, for sorting needs, the same unit may control the ejector (EJ) through an actuating circuit (AS). The sorting system uses either inter-channel (between different channels) or intra-channel (within the same channel) data processing and programming.

In the first case and as shown in Figure 10, the programming of the single units, connected together by an internal bus (IB) may occur by activating a central unit (CH) and a peripheral controller (MC). In the second case, the data from the sensors arranged on the same channel, processing in real time during descent, are analysed and processed locally by smart units (LC) which will evaluate the actuations on the basis of discrimination thresholds (TH) as shown in Figure 11.

As concerns the flow of elements to be classified/sorted, alternatively to the approach shown in Figure 2 where such objects are immersed in the guides in a continuous free-falling flow, a different methodology may be used as shown in Figure 3 (and Figure 4 right channel), wherein a mobile conveyor system (CR) positioned within each guide line is responsible for conveying the flow of objects only while the electronic devices adapted to measure and characterise the single elements remain integral with the guide itself. By exploiting the cross-correlation process of the information generated by the two sensorial typologies used, the statistic distributions related to the optical and impedimetric information characterising each type of object under examination may be identified.

In the specific case of Figure 11, the optical and impedimetric distributions are related to the different types of seeds which constitute durum wheat. These characteristic distributions result from a rather large number of samples of each type of object to be classified and are used as comparison curve to identify which family of objects each element in the flow to be sorted belongs to.

Discrimination thresholds (TH) are defined on the sample curves of the type shown in Figure 11 which identify ranges (AR) in which there are different statistic probabilities of finding the same types of objects. By combining the ranges identified in the graphs related to the optical information and those related to impedimetric information, according to an appropriate sorting algorithm, all types of objects to be sorted can be identified with a very low likelihood of error.

Therefore, the analysis method according to the present invention envisages a first self-learning step of the apparatus: during this step, the characteristic sample distributions are extrapolated and associated to each typology of object to be classified/sorted and consequently an appropriate selection algorithm is defined on the basis of the set thresholds (TH) and the resulting ranges (AR).

The second step consists in the classification itself, where each object to be identified is detected by the two sensorial typologies and the information associated thereto is compared against the sample distributions in order to identify the typology to which it belongs. The results of the classification made on the continuous flow along each guide line are used to activate sorting system integral with the lines themselves.

Object sorting, which may occur in the forms explained below, is generically called electromechanical sorting.

A first method of electromechanical sorting of the objects may be of pneumatic or mechanical nature directly on the base which accommodates the flow (B). In one case, the objects considered non-compliant to specifications (or vice versa) will be ejected using pneumatic systems (EJ) which will induce the ejection of gas from nozzles. In another possible embodiment, the ejection will be performed by mechanical action of elements which are activated by electronically controlled servo mechanisms.

An alternative method for sorting objects envisages the action of an electrical field on the objects once their flow has completed to travel the entire base (B) and therefore they are either free-falling or however beyond the area of analysis. In practice, the objects, electrostatically pre-charged before or during their flow in the base (B), will be then deviated along their course and therefore ejected by means of the action of a strong electrical field .